titus n. owl

Right, you don't have to marinade. After I wrote that post, I checked on Cook's Illustrated magazine's website (if you don't know, these guys do extensive testing to verify the reasons behind the ingredients and techniques used in recipes, and many times debunk long-held notions) and this is what they had to say:

The Problem: The flank steak is an agreeable cut of meat; even so, there are some variables to consider if you want to make the most of it. Will marinating tenderize the meat? Will it improve flavor? Or is a spice rub the way to go? Finally, is it worth waiting 5 or 10 minutes to let the meat to "rest" once it comes off the grill?

The Goal: Like other steaks cut from the chest and side of the cow, flank has a rich, full, beefy flavor. And, because it is very thin, it cooks quite quickly. All of this makes it an ideal candidate for grilling.

The Solution: Skip the marinating, which can turn the meat gray and mushy, and instead use a spice rub to impart flavor and a great crust. Cook the steak over high heat for a short period time, and use the most primitive method to check for doneness: cut it open and peek inside. Be sure to let the meat rest before slicing; this allows the juices to redistribute evenly through the meat.

Spice rubs work best on meat cooked rare. They can also work on steaks cooked medium-rare, but they need to be watched closely to keep the spices from burning. The spices on steaks cooked medium or more are almost guaranteed to burn.

In the recipes that follow this introduction, the most basic one is to just, yeah, go crazy with the salt and pepper, and grill to your satisfaction.

Oh, they also say that fajitas were originally made with skirt steak instead of flank steak; these both come from the same region of the cattle, but skirt steak is closer to the front legs, and flank steak is closer to the rear legs.